The onset of labor in women is traditionally predicted from the last menstrual period (LMP) but according to Ahmed and Klopper (1) this can be quite inaccurate because of irregular cycles, uncertain memory, and pregnancy following cessation of oral contraceptives. Work has recently been completed, by the principal investigator, in the equine species (2) which shows that the level of calcium in pre-parturient mammary secretions is an accurate predictor of the onset of labor. The primary objective of this study is to evaluate the reliability of calcium and magnesium levels in human breast secretions as an indicator of the time of onset of labor. This may also include the onset of pre-term labor. The subordinate objective is to produce an easy-to-use, non-invasive test kit which the pregnant human female will use herself, at home. Phase 1 will involve obtaining and analyzing breast secretions from approximately fifty pregnant women during late gestation. Samples will be taken on a regular basis, subjected to gas chromatographic analysis for calcium and magnesium levels, and tested with already available calcium and magnesium sensitive test strips. The results will be correlated with the onset of labor.